The present invention concerns a measuring device and in detail it concerns a device for measuring the torque of a rotation drilling machine or for measuring the force exerted by a drilling, driving or lifting machine on a tool.
It is known that machines for excavating or drilling the ground comprise devices that are commonly called rotary, for the transmission of the torque to a drilling battery at the end of which an excavation or drilling tool which typically rotates is engaged. The drilling battery typically comprises—in a non exhaustive manner—drilling rods, tubes or blades.
The rotary is moreover engaged so as to slide along a load-bearing structure, which is commonly called antenna; through suitable systems known in the field a pushing or pulling force is exerted onto the rotary and consequently to the drilling battery and therefore to the tool.
In the field of drilling machine tools, in recent years it has become a common requirement to have a performance that is always greater in terms of depth and excavation diameters obtained. This directly reflects onto the performances in terms of torque and pull-push of the machines. Consequently it is important to be able to certify and demonstrate their actual performances. The present finding concerns a device for carrying out rapid and reliable measurements of the maximum torque and pull-push that can be delivered.
From JP58098511 a device is known for measuring the dynamic torque exerted by a motor on a shaft. In particular, the device described in JP58098511 is positioned between a motor and a speed reduction unit, and does not therefore carry out a reading of the torque of a tool. Moreover, said device is a device that is integrated in a machine, and cannot therefore be used to carry out test measurements in series.
From U.S. Pat. No. 3,589,179 a device with a single arm is known for measuring the torque on drilling rods. Said device uses a compression load cell that is mounted at one end of a single arm held by a line. Said line is connected to a winch.
The device described in U.S. Pat. No. 3,589,179 is characterised in that it has the drawback of having a single measuring arm; said arm does not allow a symmetrical measurement of the torque and, in order to balance the force on the load cell, a force is created on the battery of rods which tends to flex it causing possible damage to the battery itself or wrong measurements.
Moreover, the device described in U.S. Pat. No. 3,589,179, is not adapted for measuring also load forces which are axially oriented with respect to a direction in which the excavation or drilling is being carried out. Furthermore, the patent does not describe how to dispense the maximum torque available and how to usefully oppose it. This is a critical problem in the case in which very high torque values are measured.
Finally from EP0640743 a device is known for measuring the dynamic torque on a drilling tool, or bit. Said device also measures a weight on the tool itself, and the extensometric cells which it is provided with are positioned inside radial holes that are obtained on elements of the drilling battery near to the tool itself, thus remaining constantly mounted.
Said device is not adapted for being used for testing in series adapted for detecting the torque or the maximum force that can be exerted by an excavation or drilling machine. It is, indeed, a device that is integrated with the excavation tool which does not therefore make it possible for the machine to dispense the maximum torque or pull-push. It is also very complex due to the need of having an electric rotary joint so as to transfer the signal from the rotating part to the part that is fixed to the machine. It also requires systems for compensating for temperature variations, action of the excavation fluids and effect of the flexing of the battery of rods during the excavation. All these characteristics are necessary for a device that carries out a measurement during drilling but are not useful for a testing device.